Propellant pressure burning rate slope modification

ABSTRACT

The burning rate-pressure slopes of smokeless solid propellant compositions containing butyl rubber, polytetrafluoroethylene and ammonium perchlorate, are altered by adding triphenylphosphine. Also, the burning rate of regular propellants which are not smokeless e.g., which additionally contain aluminum, are altered.

United States Patent [191 Kaufman [4 Nov. 18, 1975 [73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

[22] Filed: Sept. 25, 1972 [21] Appl. No.: 293,258

[52] US. Cl. 149/l9.3; l49/19.91; 149/20; 149/76 [51] Int. C1. COGD 5/06 [58] Field of Search 149/19, 20, 44, 76, 19.3, 149/ 19.91

[56] References Cited UNITED STATES PATENTS 11/1965 Ossyra et al. 149/19 X 3,377,955 4/1968 Hodgson 149/19 X 3,395,055 7/1968 Sparks et a1. 149/19 x 3,512,932 5/1970 Stern et a1. 149/49 X 3,513,043 5/1970 Burnside 149/49 X 3,655,836 4/1972 Dehm et a1. 149/96 X Primary Examiner-Benjamin R. Padgett Assistant ExaminerE. A. Miller Attorney, Agent, or Firm-R. S. Sciascia; Roy Miller; Lloyd E. K. Pohl [57] ABSTRACT The burning rate-pressure slopes of smokeless solid propellant compositions containing butyl rubber, polytetrafluoroethylene and ammonium perchlorate, are altered by adding triphenylphosphine. Also, the buming rate of regular propellants which are not smokeless elg., which additionally contain aluminum, are altered.

5 Claims, No Drawings PROPELLANT PRESSURE BURNING RATE SLOPE MODIFICATION BACKGROUND OF THE INVENTION relates to the burning rate modification of solid propellants and to the modification of the burning rate-pressure slope of smokeless solid rocket propellants by adding triphenylphosphine.

2. Description of the Prior Art.

It is well known that the burning rate of 'a solid rocket propellant changes with the pressure in the combustion chamber. That is as the pressure increases the rate at which the propellant burns increases and visa versa.

In some situations it is desirable that the slope of the burning rate-pressure curve of a solid propellant be very gradual. That is, it is desirable that the burning rate of the propellant not increase significantly with increased chamber pressure. One such situation is that encountered in long range rockets and the like where it is desirable to have the propellant burn over a relatively long span of time. Also, since pressure build up within a combustion chamber is directly related to burning rate, a solid propellant with a gradually sloping burning rate-pressure curve is much safer than one with a steeply sloped curve. 7

In the prior art, many burning rate modifiers, some of which provide a gradually sloping burning rate-pressure curve, have been used. However, at the present time there .is no theory available as to why various materials affect the slope 'of the burning rate-pressure curve as they do. Therefore, the selection of a burning rate modifier for use in a solid propellant must be determined by practical experimentation, particularly if it is desired to lower the slope of the burning rate-pressure CUI'VC.

SUMMARY OF THEINVENTION has also been found that triphenylphosphinemodifies the burning rate but not the slope of solid propellant compositions which contain metallic fuel particles.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following specific-Examples illustrate the effect of small amounts of triphenylphosphine on the burning rate-pressure curve of certain solid propellants. 1

EXAMPLE 1 A solid propellant containing 8 parts by weight butyl rubber, 3 parts by weight Teflon (polytetrafluoroethyl-- ene), 19 parts by weight aluminum powder and 70 parts by weight ammonium perchlorate was made up by standard methods. The propellant had a burning rate of 0.48 inch per second at IOOO-psi and a burning rate-pressure slope of 0.49.-

EXAMPLE 2 Three parts by weight of triphenylphosphine was added to the composition of Example l. The burning rate of this composition decreased significantly to 0.41 inch per second at 1000 psi but the slope of the burning rate-pressure curve remained the same at 0.49.

EXAMPLE 3 A smokeless propellant containing 7 parts by weight butyl rubber, 16 parts by weight Teflon (polytetrafluoroethylene), 77 parts by weight ammonium perchlorate and no metallic fuel was made up by standard methods. The propellant had a burning rate of 0.45 inch per second at 1000 psi and a burning rate-pressure slope of 0.57.

EXAMPLE 4 substantially absent as in smokeless propellants both the burning rate and the slope of the burning rate-pressure curve decrease significantly upon addition of triphenylphosphine.

While the foregoing Examples disclose specific basic propellant compositions and the addition of a specific amount of triphenyphosphine (3 parts by weight) thereto, it will become obvious to those skilled in the art to vary both the basic propellant composition and the amount of triphenylphosphine. For example, other binder systems could be used in lieu of the butyl rubber-fluorinated bindersystem of the Examples. Also, other oxidizers could be used in lieu of the ammonium perchlorate of the Examples. Still further, the respective parts by weight of the various propellant ingredients could be varied and additional ingredients could be added. To get satisfactory results from the particular basic compositions of the Examples, the amount of triphenylphosphine added may be varied within the range of from about 1 to about 5 parts by weight.

I claim:

1. The method of varying the burning rate-pressure curve of a propellant composition which contains 7 parts by weight butyl rubber, 16 parts by weight polytetrafluoroethylene and 77 parts by weight ammonium perchlorate which comprises:

a. providing said propellant composition; and b. adding triphenyl phosphine thereto.

2. The method according to claim 1 wherein from 1 to 5 parts by weight of triphenyl phosphine are added.

3. The method according to claim 2 wherein 3 parts by weight of triphenylphosphine are added.

4. The method for varying the burning rate of a rocket propellant composition which contains 8 parts by weight butyl rubber, 3 parts by weight polytetrafluoroethylene, 19 parts by weight aluminum and parts by weight ammonium perchlorate which comprises:

a. providing said composition; and

b. adding triphenyl phosphine thereto.

5. The method according to claim 4 wherein 3 parts by weight of triphenylphosphine are added. 

1. THE METHOD OF VARYING THE BURNING RATE-PRESSURE CURVE OF A PROPELLANT COMPOSITION WHICH CONTAINS 7 PARTS BY WEIGHT BUTYL RUBBER, 16 PARTS BY WEIGHT POLYTETRAFLUOROETHYLENE AND 77 PARTS BY WEIGHT AMMONIUM PERCHLORATE WHICH COMPRISES: A. PROVIDING SAID PROPELLANT COMPOSITION: AND B. ADDING TRIPHENYL PHOSPHINE THERETO.
 2. The method according to claim 1 wherein from 1 to 5 parts by weight of triphenyl phosphine are added.
 3. The method according to claim 2 wherein 3 parts by weight of triphenylphosphine are added.
 4. The method for varying the burning rate of a rocket propellant composition which contains 8 parts by weight butyl rubber, 3 parts by weight polytetrafluoroethylene, 19 parts by weight aluminum and 70 parts by weight ammonium perchlorate which comprises: a. providing said composition; and b. adding triphenyl phosphine thereto.
 5. The method according to claim 4 wherein 3 parts by weight of triphenylphosphine are added. 